from tkinter import *
from tkinter import ttk
def calculate(*args):
    try:
        value=float(feet.get())
        meters.set((0.3048*value*10000.0+0.5)/10000.0)
    except ValueError:
        pass


root=Tk()
root.title('英尺转换米')
mainframe=ttk.Frame(root, padding='3 3 12 12')
mainframe.grid(column=0,row=0,sticky=(N,W,E,S))
mainframe.columnconfigure(0,weight=1)
mainframe.rowconfigure(0,weight=1)
feet=StringVar()
meters=StringVar()
feet_entry=ttk.Entry(mainframe,width=7,textvariable=feet)
feet_entry.grid(column=2,row=1,sticky=(W,E))
ttk.Label(mainframe,textvariable=meters).grid(column=2,row=2,sticky=(W,E))
ttk.Button(mainframe,text='计算',command=calculate).grid(column=3,row=3,sticky=W)
ttk.Label(mainframe,text='英尺').grid(column=3,row=1,sticky=W)
ttk.Label(mainframe,text='相当于').grid(column=1,row=2,sticky=E)
ttk.Label(mainframe,text='米').grid(column=3,row=2,sticky=W)
for child in mainframe.winfo_children():child.grid_configure(padx=5,pady=5)
feet_entry.focus()
root.bind('<Return>',calculate)
root.mainloop()